Recuperative arrangement for gas turbine engines



L. l. ZIRIN Aug. 24, 1965 RECUPERATIVE ARRANGEMENT FOR GAS TUBINE ENGINES Filed June 27, 1965 INVENToR. 0H/5 A Z/,Q//V

p the power'plant.

t pliedy to the powerplant combustor. i heatexchange, the compressed fluid is heated and supf gas turbine powerplants. I gas turbine, it is essential that the engine parts be lightweight, even at the sacrifice of some thermal efficiency.

n the recuperator. been to construct recuperators with fluid tightV joints. f These joints are usually rigid and consequently prevent United States Patent O 3,201,938 RECUPERATWE ARRANGEMENT non Gas 'rUnBrNE ENGINES VLouis Isadore Zirin, Marblehead, Mass., assignor to General Electric Company, a corporation of New York Filed June 27, 1963, Ser. No. 291,150 6 Claims. (Cl. 60-39.51)

This invention relates to a recuperative arrangement for gas turbine engines and, more particularly, to a struc- 'tural arrangement for a recuperator which is relatively yincrease the thermal efficiency and thereby reduce fuel consumption. A recuperator is a heat exchanger through which high temperature low pressure exhaust tluid from the turbine is directed prior to being discharged from Inthe recuperator, the exhaust uid is passed in heat exchange relationship with high pressure low temperature compressor discharge uid which is directed through the recuperator prior to being sup- As a result of the is to increase the overall thermal eiciency of the powerplant since less fuel is required to produce a given turkbine inlet temperature.

Thermal efficiency is not, however, the only factor which must be taken into consideration by designers of For example, in an aircraft Prior 'art recuperatorsy have tended, in general, to add substantially to the weight of the powerplant. The reason for this is that the elements of the recuperator and its associated structure must be capable of containing the high pressure compressed fluid. A common way of assuring this capability is to use strong, but heavy, ele- Y ments in the recuperator, the result being a heavy recuperator. In aircraft applications, it has been found that the power required to propel the added weight of v prior art'recuperators can more than offset the savings in thermal eiiiciency.

f In addition to the weight consideration, leakage of the compressed fluid into the exhaust fluid in the recuperator can be a problem in View of the substantial pressure difference between the two fluids. In the event that such leakage occurs, there is a complete loss to the sys- It will thus be obvious that a significant efficiency which would otherwisebe obtained by use of To prevent leakage, the practice has normal thermal` expansion and contraction of the recuperator elements in response to temperature changes.

. With thermal expansion and contraction thus restrained, ythe elements of the recuperator are subjected to undesirable thermal stresses. In time, these stresses can age ,decreasing substantially the thermal efciency of the Powerplant. t

It is therefore a primary object of this invention to yprovide an improved recuperative arrangement for gas ice turbine powerplants which is relatively lightweight and substantially free of thermal stresses.

It is another object of this invention to provide a recuperative arrangement which has low leakage without having substantial thermal stresses.

A further object of this invention is to provide a recuperative arrangement which is simple in design and relatively easy and inexpensive to manufacture.

Briefly stated, in accordance with an illustrated embodiment of the invention, a gas turbine powerplant is provided with a heat exchanger, or recuperator, in the passageway connecting the turbine to the Powerplant discharge opening. In the recuperator, the exhaust fluid from the turbine is passed in heat exchange relationship with compressed uid ducted from the discharge portion of the Powerplant compressor. From the recuperator, the heated compressed fluid is directed to the inlet portion of the powerplant combustor. More particularly, the recuperator connects first and second headers in uid ow relation, one of the headers being enveloped by the other header. First and second ducting means are connected to the rst and second headers, respectively. As in the case of the headers, one of the ducting means is enveloped by and coaxial with the other ducting means. One of the ducting means is connected to the discharge portion of the compressor and the other ducting means is connected to the inlet portion of the combustor. Since there is little pressure drop within the recuperator, the pressure is substantially the same within the inner and outer headers and the inner and outer ducting means. As a result, the inner header and the inner ducting means need not be of particularly strong construction. Also in view of the very slight pressure difference across the inner elements, expansion joints may be provided in the inner ducting means without risk of excessive leakage.

While the invention is distinctly claimed and particularly Pointed out in the claims appended hereto, the ininvention, both as to organization and content, will be better understood and appreciated, along with other objects `and features thereof, from the following detailed description when taken in conjunction with the drawing, in which:

FIG. 1 is a view, partially in section, of a gas turbine Powerplant incorporating the recuperative arrangement of this invention; and

FIG. 2 is a sectional view of the recuperative portion of the gas turbine Powerplant illustrated by FIG. 1; and

FIG. 3 is an enlarged View of one of the heat exchange members comprising the recuperator; and

FIG. 4 is a view taken along line 4 4 of FIG. 3; and

FIG. 5 is a view similar to FIG. 1 of a portion of a gas turbine Powerplant having a bypass arrangement for selectively bypassing the `recuperator of this invention.

Referring now to the drawing, and particularly to FIG. l, a gas turbine Powerplant indicated generally by numeral 1@ is illustrated. The Powerplant 10 includes in axially spaced relation an axial ow compressor 11,

, A Propeller 18 is driven by the power turbine 14 through a shaft 19 coaxial with the shaft-17.

The exhaust passageway 15 connecting the power turbine 14 andthe discharge opening or nozzle 16 is defined` between an outer casing 20 and an inner exhaust casing 21. The exhaust fluid flowing through the passageway 15 is directed over the outer surfaces of a large number of axially extending heat exchange members 22, the flow path of the exhaust fluid being shown by the arrows Y chargedk from the in FIGS. 1 and 2. Each of the heat exchange members 22 is connected to a header arrangement comprised of 'may be provided in the conduits-27. The expansion joints 50 must be strong enough, however, to contain the high anouter annular header 23 encircling the powerplant 10 and an"inner'annular header 24 enveloped by the outer header 23. A pluralityrof tubular conduits25 connect the discharge' portion 26 Kof the compressor 11 to the inner header 24, anda plurality of tubular conduits27 connect the inlet portionk 28 of the combustor 12 tothe 'Y outer header 23. Each of the Yconduits' 25 is enveloped by and is coaxial withja corresponding one', of the conduits 27 as best shown by'FIG. 2. Annular wall means 29 as illustrated by FIG. 1 are locatedin the'passageway connecting the discharge portion.26 ofthe'compressor 11 to the inlet' portion 28 of the combustor 12 `to block the passagewayand prevent ilow f 'compressor discharge fiuid directly to the `combustor 12. The wall bers `22 is illustrated by FIGS. 2 4, the -details' of con- Y lstruction being '-shown' by FIGS. 3-'and 4.V As shown,

pressure compressed fiuid. 'Y f As in the casey of the tubular conduits 2,5, the inner annular header 24 has substantially the same pressure acting on its innerand outer surfaces.. As a result, the inner header 24 can be of relatively lightweight construction. The outer header 23 is, likev the outer conduits 27, of relatively heavy construction capable of containing the highpressure fluid. It willy thus be seen that the arrangement of this invention'requires that only one of the headers and only one set of the conduits be strong enough to withstand VVthe .full pressure rof thecompressed uid. The'total weight of the recuperator is thus reduced substantially from what would be required if both headers and both sets of conduits -were subjected to the full pressure of thecompressed fluid. Y

Thermal expansion and contraction 'of-the elements of Ythe heatYexchange members 22.y may also occur. without creating thermal stresses.' As best illustrated by`FIG.v 3,

Itheycylinders 40 are secured to both the outer'header 23 l andthe inner *header 24, the cylinders 40 thus supporting each member 22 includes anY elongated cylinder 40hav'- ying ia coaxial tube 41 mounted therein. The downstream 4end ofthe cylinder 40 is closed by a cover 42, and the Ytube41 terminates at'itsdownstream end just short of 'the cover 42 such that a fluid passageway is provided between the interior of the tube 41 andthe space'43 between'the tube 41 andthe cylindner 40. Therupstream 'end ofthe tube 41 Vextends through a plate 44 jonthe upstream end of the cylinder 40- into the interior. of the inner annular headerr24.vv As best shown by FIG. 4, the

Vtube 41is slidablymounted within the cylinder 40 byr relative axial movement between the cylinders -40 and 46.

' The upstream en d of the cylinder40 issecured to both the outer annular header 23 and the inner' annular header v 24 by suitable: means Vsuch as the welds shown by'FIG. Y i 3, and orifices'48 connect the interior of the outer header 23V and the space 43 in uid flow relation. y Y

The operation of the recuperatorwill now be described.

High pressurev compressedV fiuid from the discharge porr-r thev inner header.` Thermal expansion or contraction of the cylinders40 thus results in slight movement of the inner header 24 relative pto the youterheader.' Since the Y slip joints 49 are provided inthe conduitsjZS, nostresses are createdr vby themovement of the inner header. The finned structures 45 'and"47 ypermit free thermal expansion andV contraction between the tubes41- vand the associated cylinders 40 and 46 Y .Y The total weight of therecuperator isv also affected by its size j Y It will be notedv that the vrecuperative arrangement illustrated by FIG.Y 1 .directs iall. ofthe exhaust fluid andccmpressed'air through 'the -recuperator under all operating conditions. :rIt is 'therefore va requirement VV'that'therecuperator Ybe large enough to handle' the maxifinned structure 47 supports the cylinder 40 Y'and permits Avr mum flow'jrates ,f which occur 4,when the powerplant'is 'operating underk full load conditions; At part power Operation, the .capacityY and weightY of the recuperator are 40 greaterfthanrequired at: partpow'er. This typey of engine "ismostefiicient'when operating at fullpower. Some en- YV`gines are, howevennormally run atl part power settings. y It is therefore sometimes desirable to design the recuperator toi'provide most eiiicient operation at partpower. A

recuperative Yp'owe'rplant utilizing rthisv invention for efy ficientpart power operation is illustrated by FIG.l 5.

tion 26eofthe compressor 11 vis directed through con- Y *f duits 25 to the inner lannular header y24, from; which 1 theiluid enters the tubes 41 ,andr ows throughY the; heat Y, exchange memberr22 asl rshown by the arrows in FIG. 3j.

The compressed fiuid is heatedas it flows through theV tube 41 and the closed cylinder 40 bythe exhaust uid Y flowing over theouter surface of ,thecylinder40g-f The heated fluid is dischargedfrom the space 43 through the orifices 48`into the interior" orftheoutergheader 23, from whichit fiows through the conduits 27 to the inlet'portion 28 of the combustor 12.' -The cooled'exhaust fluidis dis'f Y 'Y powerplantl 10 kthrough, the discharge nozzle16. A l

YIt will 'be obvious to those skilled in the art thatrthe compressed rfluid in the conduits,- 25 is at "approximately thei'same Vpressure as theheatedilui-d in Athe `conduits 27.

As a result, the conduits y25 can be vof relatively lightweight construction having strength sufficient to withstand the pressure difference between thehudinthe coaxialpcon-r duits. Similarly, inview Aoithesmall pressure'ditference InFIG. '5, a gas turbine r powerplant 10 is illustrated,

f thell'powerplant10 being substantially similar tothe vp'ovverplant 10 of FIG- 1. The uid handlingelements "comprising the recuperator are,r'however, sized to accom- Ymodate only `aportion of the full loadl gas flow. Theelements are thus substantially flighter'than 'the counterpart part power operation, all of the'exhaust Atluidfisv directed over the'fouter surfaces of the heat exchange;l members 22. y'When Vthe exhaust owuis greaterthancan beV acconimdated'thr'oughthe exhaust passageway 15', valve 'platesY60 'aremoved from the closed'positions illustrated E byrsolid4 lines in* FIGJS tothe open positions illustrated byfbroken lines;y With the Valve'platesl) in the open '.positions, ythe excess flowfat-high power settings can be 'bypassed' around 'the-recuperator and discharged through the nozzle 1'6. i This "arrangement isthusmost efficient 6Y5"iatV normal part power operation.

' Y cuperative arrangement Vof this invention'` provides a rela- From the foregoing, :itwillbe appreciated that the retivelylightweight structure which' is substantially freeof thermal stresses.y 'The arrangement also provides a struc. ture having inherently 'low leakage.

It willbe understood that the'invention-is not limited tothe specific 'details' of 'construction' and-'arrangement of theembodiments illustrated and describedherein since changes 'and modifications will b'e obvious to those skilled inthe art; Forexample,*thetubular conduits 25 4and27 maybe replaced with-complete annular ducts encircling the powerplant, one of the ducts being enveloped by the other. Similarly, although the illustrated embodiment is preferable, the headers 23 and 24 need not extend around the entire periphery of the powerplant. It is therefore intended to cover in the appended claims all such changes and modifications which may occur to those skilled in the art without departing from the true spirit and scope of the invention.

What is claimed as new and desired to secure by Letters Patent of the UnitedStates is:

1. In a gas turbine powerplant including a fiuid cornpressor having inlet and discharge portions, a combustor having inlet and discharge portions, and a turbine having inlet and discharge portions in axially spaced relation, a discharge opening, and a passageway connecting the discharge portion of the turbine to the discharge opening, a recuperative arrangement comprising:

a first annular header,

first ducting means connected to said first annular header,

a second annular header enveloped by said first annular header in spaced relation thereto,

second ducting means connected to said second annular header,

said second ducting means enveloped by and coaxial with said first ducting means,

one of said first and second ducting means connected to the discharge portion of the compressor and the other of said first and second ducting means connected to the inlet portion of the combustor,

and a bank of heat exchange members positioned in the pasasgeway between the discharge portion of the turbine and the discharge opening in heat exchange relation with combustion products fiowing therethrough,

each of said heat exchange members comprising an elongated closed cylinder slidably supported in the passageway and a coaxial tube slidably supported within said cylinder,

said elongated cylinder intersecting the wall of said first annular header and secured to said first and second annular headers adjacent first ends of said cylinder and said tube, said elongated cylinder supporting said second annular header within said first annular header,

the first end of said tube intersecting the wall of said second annular header and opening into the interior of said second annular header,

means defining a fluid passageway adjacent the first ends of said cylinder and said tube between the interior of said first annular header and the space between saidv cylinder and said tube,

means defining a fiuid passageway adjacent the second ends of said cylinder and said tube between the interior of said tube and the space between said cylinder and said tube,

whereby fiuid supplied to said heat exchange members from the compressor is heated by the combustion y bine to the discharge opening, a second passageway connecting the turbine to the discharge nozzle, and a valve in the second passageway movable between open and closed positions, the entire flow of combustion products being directed through the first passageway when the 6 valve is in its closed position, a' recuperative arrangement comprising:

a first annular header,

a first set of tubular ducts connected to said first annular header,

a second annular header enveloped by said first annular header in spaced relation thereto,

a second set of tubular ducts connected to said second annular header,

each of said second set of ducts enveloped by and coaxial with a corresponding one of said first set of ducts,

one of said first and second sets of ducts connected to the discharge portion of the compressor and the other of said first and second sets of ducts connected to the inlet portion of the combustor,

and a bank of heat exchange members positioned in the first passageway between the discharge portion of the turbine and the discharge opening in heat exchange relation with combustion products flowing therethrough,

each of said heat exchange members comprising an elongated closed cylinder slidably supported in the first pasageway and a coaxial tube slidably supported therein,

said elongated cylinder intersecting the wall of said first annular header and secured to said first and second annular headers adjacent first ends of said cylinder and said tube, said elongated cylinder supporting said second annular header within said first annular header,

the first end of said tube intersecting the wall of said second annular header and opening into the interior of said second annular header,

means defining a fiuid passageway adjacent the first ends of said cylinder and said tube between the interior of said first annular header and the space between said cylinder and said tube,

means defining a fiuid passageway adjacent the second vends of said cylinder and said tube between the interior of said tube and the space between said cylinder and said tube,

whereby fiuid supplied to said heat exchange members from said compressor s heated by the combustion products fiowing through the first passageway prior to being delivered to said combustor.

4. A recuperative arrangement for a gas turbine powerplant as defined by claim 3 in which first and second expansion means are provided in said first and second ducting means, respectively, to accommodate expansion and thereby relieve stresses therein.

5. In a gas turbine powerplant including a fiuid compressor having inlet and discharge portions, a combustor having inlet and discharge portions, and a turbine having inlet and discharge portions in axially spaced relation, a discharge opening, and a passageway connecting the discharge portion of the turbine to the discharge opening, a recuperative arrangement comprising:

a first annular header,

a second annular header enveloped by said first annular header in spaced relation thereto,

a heat exchanger connecting said first and second annular headers in fiuid flow relation,

said heat exchanger positioned in the passageway between the discharge portion of the turbine and the discharge opening in heat exchange relation with combustion products flowing therethrough,

first ducting means connected to said first annular' header,

and second ducting means connected to said second annular header,

said second ducting means enveloped by and coaxial with said first ducting means,

one of said first and second ducting means connected to the discharge portion of the compressor for sup- 7 rplyingr compressor discharge fluid to said heat eX- changer and the other of ysaid rstand second ducting meansconnected to the inlet portion of the combustor, for` supplying the heated 4compressor discharge uid tothe combustor from said heat exchanger,

the pressure of compressor discharge fluid in said first and second ducting means, said first and second headers, and said"4 heat'` exchanger being substantially uniform such that said second, header and said 'sec-w 'ond ducting meansware. subjected rtoisubstantially balanced internal andexternal pressure during power-V plant operation,

thefrelatively small pressure gradients existing acrossy saidsecond'header and said second ducting meansv L '15 v during powerplant operation permitting the use of relativelyy lightweight and klow-strength materials in the fabrication of'said members.

6. In a gas turbine powerplant including'a iidcompressor having inlet' and discharge portions, a combustor having inlet and discharge portions; and al turbine having inlet and discharge portionsin axially spaced relation, a Adischarge opening, and a passageway Yconnecting the discharge portion ofthe turbine lto :the discharge opening,

' a recuperative arrangement` comprising:

' a first annular header, Y

a second annular header enveloped by said nular header in ,spacedrelation thereto,

irst ana bank of composite, expansible heatexchange members connectings'aidfirst and secondannularheaders in uid flow relation, t

said vbank of composite heat'exchange .members positionedin the ypassageway ,betweenv the discharge portion ofthe turbine and thedischarge opening in heatfexchange relationfwith combustion prodnctsj owingtherethrough, Y iirst ducting means connected to4 vsaid first vannular header, l and second' ducting means Yconnected* to said second annular header, Y

VVT,said-second ,ductingmeans venveloped by and coaxial ,with said first rductingmeans,`

' onepof said iirst'and second ductingyineansconnected tothe-discharge'portion of the compressor fork sup- Vplyingmcompressor ydischarge uid to-)said heat .exchange members and thev other yof said first Aand sec- 'o'nd Iducting means connected to -the inlet portion of the, combustor for supplying the heated compressor Ydischarge fluid tothe' combustor from said heat exchange members., v

l the-pressure'of-compressor discharge uid in said Vfirst j and second lducting means, saidY first and second headers, Yand said heat exchange members kbeing rsuby ,stantially uniform Asuch thatsaid second header and i Y References Cited'by'th'e Examiner v fU-ENITEDv STATES PATENTS VFOREIGN PATEisrrsv V604,114, s/4s Great Britain. SAMUEL LEX/INE, Prrz'mary Examiner. 

1. IN A GAS TURBNE POWERPLANT INCLUDING A FLUID COMPRESSOR HAVING INLET AND DISCHARGE PORITONS, A COMBUSTOR HAVING INLET AND DISCHARGE PORTIONS, AND A TURBINE HAVING INLET AND DISCHARGE PORTIONS IN AXIALLY SPACED RELATION, A DISCHARGE OPENING, AND A PASSAGEWAY CONNECTING THE DISCHARGE PORTION OF THE TURBINE TO THE DISCHARGE OPENING, A RECUPERATIVE ARRANGEMENT COMPRISING; A FIRST ANNULAR HEADER, FIRST DUCTING MEANS CONNECTED TO SAID FIRST ANNULAR HEADER, A SECOND ANNULAR HEADER ENVELOPED BY SAID FIRST ANNULAR HEADER IN SPACED RALATION THERETO SECOND DUCTING MEANS CONNECTED TO SAID SECOND ANNULAR HEADER, SAID SECOND DUCTING MEANS ENVELOPED BY AND COAXIAL WITH SAID FIRST DUCTING MEANS, ONE OF SAID FIRST AND SECOND DUCTING MEANS CONNECTED TO THE DISCHARGE PORTION OF THE COMPRESSOR AND THE OTHER OF SAID FRIST AND SECOND DUCTING MEANS CONNECTED TO THE INLET PORTION OF THE COMBUSTOR, AND A BANK OF HEAT EXCHANGE MEMBERS POSITIONED IN THE PASSGEWAY BETWEEN THE DISCHARGE PORTION OF THE TURBINE WITH CUMBUSTIN PRODUCES FLOWING THERETHROUGH, EACH OF SAID HEAT EXCHANGE MEMBERS COMPRISING AN ELONGATED CLOSED CYLINDER SLIDABLY SUPPORTED IN THE PASSAGEWAY AND A COAXIAL TUBE SLIDABLY SUPPORTED WITHIN SAID CYLINDER, SAID ELONGATED CYLINDER INTERSECTIN THE WALL OF SAID FIRST ANNUALAR HEADER AND SECURED TO SAID FIRST AND SECOND ANNULAR HEADERS ADJACENT FIRST ENDS OF SAID 